Here is a good lab to check the observational skills of your students. I do this early in the year so I can check my class procedures for lab clean up. The students will also see something that is not expected, which adds to the excitement. The students will also have some practice measuring with a graduated cylinder.

To do this, measure 25 ml of half and half and pour into a perti dish. Put one or two drops of four different colors of food coloring into the half and half. Then put a match into a drop of Joy Ultra dish detergent and then put into the middle of the colors. The colors will move to the outside and then start to blend together. You can adapt this to almost any grade level.